Charles f



UNITED STATES PATENT OFFICE.

CHARLES F. BURGESS, 0F MADISON, WISCONSIN, ASSIGNOR TO BURGESS BATTERY COMPANY, OF MADISON, WISCONSIN, A CORPORATION OF WISCONSIN.

MANUFACTURE OF DRY CELLS.

No Drawing.

To all whom it may concern: I

Be itknown that I, CHARLES F. BURGESS, a citizen of the United States, residing at Madison, in the county of Dane, State of Wisconsin, have invente certain new and useful Improvements in the Manufacture of Dry Cells, (Case I;) and I do hereby der clare the following to be a full, clear, and

exact description of the invention, such as yielding oxygen to lessen polarization. The

material which has been the standard for this work has been the high'grade pyrolusite\ ore o tained from Russia and, analyzing about 5% MnO and less than 1% of iron, and before using has usually been ground to a 20-mesh size or finer.

- of this material.

.I have found that the ampere hour capacity of a' dry cell is dependent not only on the percentage of MnO in the depolarizing material, butalso upon the physical condition A hard, dense ore gives less satisfactory results than a softer, po-

centage of M110 and I have discovered a way of treating manganese oxid ores,'-preparatory to use in dry cells, whereby their efficiency as a dry cell material is very much increased and whereb even hard, dense ores are made to give resu ts as good or even better' than the softer material, heretofore obtainable. r

The process of my present invention comprises a roasting of the manganese oxid ore to convert some of its manganese dioxid to a lower oxid, and then treatingwith a suitable solvent to dissolve out Said' lower oxid and leave a porous residue of relatively pure manganese dioxid. Theroasting operation may be carried out'as a step preliminary to the removal of various im urities, such as arsenic, antimony, nickel, c romium, cobalt copper, as described and claimed in my Application filed October 20,

Specificationbf Letters Patent. Patented June 3, 1919.

1917. Serial No.197,55 8.

companion application, Serial No. 197,554 filed October 20, 1917, or may\be'carried out solely for the purpose of rendering the manganese dioxid more porous and thereby -more efficient.

I prefer to roast for about one to four hours at a temperature of about 600 C., as

I have found that this converts suflicient of the MnO to a lower oxid. The ore may be ground to a size of 20-mesh or finer, either before or after roasting. 1 1

The treatment for removal of the lower oxid may be effected with an aqueous solution and preferably is effected with a dilute mineral acid, such as a 10% sulfuric acid or an equivalent solution 'of niter cake -(NaHSO or a 5% hydrochloric acid. The lower oxids of manganese are more soluble than manganese dioxid. and so pass into solution as chlorids, if dr'ochloric acid is used, or as sulfates, if su furic acid orniter cake is used, so that on washing and drying the residue, there is obtained a-relatively' pure or high grade manganese dioxid. Vanous impurities, such as arsenic, antimony,

nickel chromium, cobalt and copper, may

likewise be removed by a solvent, and their removal increases the porosity of the residue and at the same time improves. its quality.

Under high magnification the individual grains of the residue are highly porous, somewhat like pumice stone or sponges, and

each grain presents an enormous total area exposed to the action of the electrolyte and other ingredients of the dry cell.

When using a mineral acid solution as above mentioned for this treatment, I find that purification is substantially complete with dense 20-mesh material after agitation with the. solvent for one to eight hours. This treatment can be carried on at room temperature or can be hastened by heating.

In making dry cells out of manganese oxid ore rendered porous by roasting and subsequent acid treatment, I proceed according to well known methods, mixing the manganese dioixid with carbonaceous material,

and carbon, together with an electrolyte of sal-ammoniac-zinc chlorid, and assembling the materialsbetween the electrodes of the cell in well known manner. By this process, the hard, dense ores may be utilized with resuch as graphite or a'mixture of graphite sults equal to and, in some instances, superior to those obtainable with softer grades.

I claim:

1. The method which consists in roasting a manganese oxid ore to convert some of its manganese dioxid to a lower oxid', dissolving out said lower oxid to leave a porous residue of relativelypure'manganese dioxid, and intimately mixing said residue with a suitable carbonaceous material to form a depolarizing suitable for use in dry cells. 2. The method which consists in roasting a dense manganese oxid ore at a temperature of about 600 C. for about one to four hours to convert some of its. manganese dioxid to a lower oxid', dissolving out said lower oxid -to leave a porous residue of relatively pure manganese dioxid and intimately mixing said residue with a suitable the roasted ore with a dilute mineral acid to dissolve out said lower oxid and leavea porous residue of relatively pure manganese dioxid and intimately mixing said residue with a suitable carbonaceous material to form a depolarizing mix suitable for use in dry cells.

4. A depolarizing mix for dry cells, comprising a carbonaceous material intimately associated with manganese dioxid rendered porous by dissolving out a lower oxid formed therein by prellminary roasting.

5. A depolarizing mix for dry cells comprising a carbo'naceousmaterial intimately associated with manganese dioxid rendered porous by dissolving out with a dilute mineral acid a lower oxid' formed therein by preliminary roasting to about 600 C.

In testimony whereof I aifix' my signature.

CHARLES F. BURGESS. 

